This invention relates to flexible polyurethane foam containing copper, to methods of incorporating the copper into the foam and to the use of the foam in articles for alleviating discomfort experienced by people who suffer from an ailment associated with joints, limbs and muscles, such as arthritis and rheumatism.
It is known that copper has antifungal properties. Thus, GB-A-1581586 discloses a sock having, adhered to its inner surface, a composition comprising a water-insoluble resin binder and, dispersed in the binder, a metal powder. The metal may be copper and the binder may be a polyurethane. The composition may additionally contain what is referred to as a xe2x80x9cfoaming agentxe2x80x9d to allow foaming of the composition after its application to the sock so as to improve softness and air and moisture permeability. However, the only example given of such a foaming agent is of capsules of a vinylidine chloride/acrylonitrile copolymer which expand on heating. This will not cause the binder to foam. It is suggested that sweat fat and other substances release the metal from the resin and convert it to soluble ionic substances.
GB-A-2133287 discloses an adhesive plaster having a surface, for contact with the skin, provided with strips of adhesive and between the strips of adhesive a metal or metal alloy, e.g. copper. The copper apparently relaxes muscle spasms caused by a wide variety of diseases, including rheumatism; sweat, formed by application of the plaster, serves as an electrolyte between grains of the metallic substance and generates an electrolyte current which intrudes under the skin surface or into the muscles lying underneath.
It is known to incorporate very small amounts of copper dust, cupric oxide, cuprous oxide or copper sulphate solution into a polyurethane foam to serve as a flame retardant, as described by B. C. Levin et al in Plastics Compounding (January/February 1990), 13(1), 58-62. In particular, cuprous oxide is added to the polyol from which the polyurethane foam is prepared in an amount of 0.072%.
It is also known to incorporate, into polyurethane foam, small amounts of copper in the form of copper salts and complexes thereof to achieve certain effects, e.g. as a catalyst during the production of polyurethane and as a smoke suppressant in flame retardant foams; see U.S. Pat. No. 4,263,411, which recommends the incorporation, in-situ, into the foam of the copper salt or complex so as to provide about 0.05 to about 3 parts (based on metallic copper) per 100 parts by weight of the polyol used to prepare the foam.
However, copper and its compounds display amphoteric properties. Thus, in conventional flexible polyurethane foams, the addition of copper powder can lead to retardation of foam cure, even at relatively low levels, and especially in low density high water formulations can lead to excessive scorching and, possibly, runaway exothermic conditions which could result in spontaneous combustion of the foam.
Moreover, we have found that even if attempts are made to introduce copper into the foam by impregnation with a slurry of copper, at higher levels of copper, there is a serious degradation in the heat ageing properties of the foam, for example, on drying the foam.
We find surprisingly that a particular useful application of flexible polyurethane foam, containing copper or copper oxide particles, but especially foam containing relatively large amounts of copper or copper oxide particles lies in the alleviation of discomfort of people suffering from various joint, limb and muscle ailments such as arthritis and rheumatism.
We also find surprisingly that such relatively larger amounts of copper or copper oxide particles can be incorporated into a flexible polyurethane foam if the polyol used to prepare the polyurethane is of a high reactivity and high molecular weight, as hereinafter defined, so that the resultant flexible foam may be of the xe2x80x9chigh resiliencexe2x80x9d or xe2x80x9ccold curexe2x80x9d type.
Thus, according to one aspect of the invention, there is provided a flexible polyurethane foam having, incorporated therein, particles of copper or copper oxide in an amount, based on metallic copper, of at least 1% by weight of the total weight of the metallized foam.
More preferably, the amount of copper or copper oxide particles, on the above weight basis, is at least 2%, still more preferably at least 3.5% and especially at least 4%.
The particles may be in the form of a powder or flake and are preferably of copper. Typically, the particle size may be from 10-100, preferably 30-60 microns, e.g. 40-50 microns.
The polyurethane is preferably derived from a polyol having a molecular weight of at least 3,500, more preferably at least 4,000, still more preferably from 4,000-8,000, especially from 4,500-7,000, more especially 4,800-6,000.
The hydroxyl value is preferably 20-60, more preferably 22-45, still more preferably 24-38, mg KOH/g.
It is also preferred that the polyol has an equivalent weight of from 1,000-3,000, more preferably from 1,500-2,000. This provides improved foam stability, flexibility and resilience.
It is especially preferred that the primary hydroxyl content, as a % of total hydroxyl content, hereinafter sometimes referred to as the primary:secondary hydroxyl ratio, provided by the hydroxyl groups in the foam be at least 20%, more preferably at least 50%, still more preferably at least 70%, most especially preferably at least 80%.
It is also especially preferred to use polyether polyols (or mixtures thereof) or polyester polyols (or mixtures thereof), particularly a polyether polyol which is an adduct of at least one low molecular weight polyol having at least 3 hydroxyl groups, such as glycerol, sorbitol, trimethylol propane or pentaerythritol, as polyol starter, with a mixture of propylene and ethylene oxides, which form polyether chains.
Tipping with ethylene oxide provides primary sites and the greater the proportion of such sites, the greater the reactivity of the polyol.
Thus, in order to provide an especially preferred, highly reactive polyether, either propylene oxide alone (required in any event at least to provide sufficient insolubility in water) or a mixture thereof with ethylene oxide are first reacted with the polyol starter to form polymerized chains which are then end-capped by reaction with further ethylene oxide to increase the reactivity considerably.
Particularly preferred polyether polyols are so-called xe2x80x9cmodified polyether polyolsxe2x80x9d, which contain organic fillers formed by the in-situ polymerization of suitable monomers and which fall into three classes, namely,
(1) polymer polyols;
(2) PHD polyols; and
(3) PIPA polyols.
In such polyols, in addition to the polyether polyol itself, the polyol contains at least one other polymer dispersed therein. Thus, a polymer polyol additionally includes a vinyl polymer dispersion, formed in situ in the polyol, as well as the reaction product of a polyol and a vinyl monomer. A PHD polyol contains a dispersion of a polyurea in the polyether polyol, formed in situ by polymerization of a diamine and an isocyanate, while a PIPA (polyisocyanate polyaddition) polyol contains a polymer dispersion formed by reaction of an alkanolamine with an isocyanate.
Such modified polymers are described more fully in xe2x80x9cTelechelic Polymers: Synthesis and Applicationsxe2x80x9d, Ed. E. J. Goethals, CRC Press Inc., Florida, 1989.
We find surprisingly that the polyurethane foams prepared from highly reactive polyols having a high primary:secondary hydroxyl ratio as described above are less susceptible to retardation of foam cure during their preparation and less susceptible to degradation in the heat ageing properties of the final foam.
Typical commercially available polyols for use in the incorporation, in situ, of copper into a polyurethane foam during its preparation are
1. DESMOPHEN 7653xe2x80x94a PHD (polyurea dispersion) polyol, which is a 10% dispersion of polyurea particles in a 6000 M.Wt.polyol, with a hydroxyl number 28 and a primary:secondary hydroxyl ratioxe2x89xa750%, commercially available from Bayer.
2. DESMOPHEN TP. PU 44WB03xe2x80x94a 6000 M.Wt.polyether polyol, having a hydroxyl value of 28 and a primary:secondary hydroxyl ratioxe2x89xa750%, commercially available from Bayer.
3. SPECFLEX NC635xe2x80x94a polyol based on glycerol and a higher functionality polyol as polyol starters and capped with ethylene oxide. It has a molecular weight of 6000, a hydroxyl number of 28, an ethylene oxide content of 14% and a primary:secondary hydroxyl ratio of 80%. It is commercially available from Dow.
4. VORANOL 6008, a polyether polyol having a molecular weight of 6000, an ethylene oxide content of 14-15% (end-capped) and a primary:secondary hydroxyl ratio of 80%. It is commercially available from Dow.
High molecular weight, high reactivity polyols, such as those described above, allow the production of a lightweight foam which is of an open celled and porous nature, allowing it to breath and reduce the incidence of perspiration.
The polyurethane of the flexible foam is preferably derived from an isocyanate selected from toluene diisocyanate, diphenylmethane diisocyanate and a modified and polymeric diphenylmethane diisocyanate and mixtures thereof.
When the isocyanate is toluene diisocyanate, it may be a mixture of 2,4- and 2,6-toluene diisocyanate in a molar ratio of 2,4-:2,6- of 80:20 or of 65:35, each of which mixtures is commercially available. Alternatively, these respective mixtures may be blended to provide any derived ratio of 2,4-:2,6- isomers within the range 80: 20 to 65:35 and thereby influence the stability and cell opening effect of the final foam as derived.
However, more preferably, the isocyanate is a diphenylmethane diisocyanate (MDI) or a modified MDI or polymeric MDI. Such MDI type isocyanates are commercially available, e.g. the Voranate series available from Dow and the Lupranate M series available from Elastogran (UK) Ltd.
Highly reactive polyols, as described above, together with MDI type isocyanates react to form so-called high resilience polyurethane foams, an added advantage of which is their greater resistance to ignition.
The polyurethane foam is preferably prepared using water as the foaming agent, more preferably in an amount of from about 1 to 7 parts by weight per 100 parts by weight of the polyol component.
In addition to the foaming agent, other additives may be present in the reaction mixture and may be incorporated within the foam.
Typically a reaction mixture can include any one or more of the following components, namely an auxiliary blowing agent, catalyst, surfactant, filler, chain extender, crosslinker, stabilizer, antistatic additive, colourant and antioxidant, and indeed more than one of any such component may be present.
In addition, the incorporation of flame retardant additives such as melamine, aluminium trihydroxide, ammonium polyphosphate, expandable graphite, halogenated phosphates, etc, produces foams having increased flame retardant properties.
The above method can be used to manufacture slabstock foam in a well known manner, using a continuous or discontinuous process. Moulded foams can also be produced.
The resultant foam preferably has a density of from 15 to 120 kg/m3, more preferably from 30 to 80 kg/m2, inclusive.
According to ASTM D1056-1985, a flexible foam is defined as a cellular structure which will not rupture within 60 secs. when a specimen 200xc3x9725xc3x9725 mm is bent around a 25 mm mandrel at a uniform rate of one lap in 5 secs. in the form of a helix at a temperature between 18 and 29xc2x0 C.
The amount of copper or copper oxide (expressed as metallic copper) in the metallized foam is at least 1%, preferably at least 2%, more preferably at least 3.5% and especially at least 4%, by weight of the total weight of the foam. However, it may be as high as 40%, 50% or even 60% by weight.
At least up to amounts of 25% by weight, incorporation of the copper or copper oxide into the foam can be achieved by an in-situ process (where the particles are incorporated in a polyol component of the polyurethane reaction mixture, as later described), while even larger amounts, for example up to 60%, may be achieved by impregnation (which technique is preferred to the in-situ method for amounts of at least 20% by weight).
Thus, according to another aspect, the invention provides a method of incorporating, into a flexible polyurethane foam derived from a polyol and a polyisocyanate, particles of copper or copper oxide in an amount of at least 1% by weight of metallic copper, by weight of the total weight of the metallized foam, which method comprises mixing the metal with the polyol and reacting the polyol with the polyisocyanate in the presence of a foaming agent to form the flexible polyurethane foam, whereby copper or copper oxide particles are incorporated in-situ within the foam.
According to yet another aspect, the invention provides a method of incorporating, into a flexible polyurethane foam, particles of copper or copper oxide in an amount of at least 1% by weight of metallic copper, by weight of the total weight of the metallized foam, which method comprises forming a slurry of the particles of copper or copper oxide in a polymer latex medium and treating the foam with the said slurry to allow impregnation of the copper or copper oxide into the foam.
Typically, the polymer latex is a latex of an acrylic polymer which may contain from 40 to 80%, preferably 50 to 60%, especially about 55%, by weight of solid polymer as well as a dispersing and/or wetting agent, an antifoaming agent and a thickener.
Except where particularly high levels of copper are required, a preferred product, at least in terms of reduced density and improved porosity, can be manufactured more economically by the in-situ method.
As mentioned above, we have found surprisingly that foams loaded with copper are capable of alleviating discomfort associated with, for example, arthritis.
Thus, according to another aspect, the invention provides an article for alleviation of discomfort from an ailment associated with a joint, limb or muscle, such as rheumatism or arthritis, which article comprises a flexible polyurethane foam covered by a fabric, which flexible foam has, incorporated therein, particles of copper or copper oxide, in an amount, based on metallic copper, of at least 1% by weight of the total weight of the metallized foam.
Preferably, the amount, based on metallic copper, is at least 2%, more preferably at least 3.5%, still more preferably at least 4%, by weight of the total weight of the metallized foam.
When obtained by the in-situ method as described above, amounts of copper and copper oxide, based on metallic copper may be 2 to 60 parts, preferably 2 to 50 parts, more preferably 2 to 40, still more preferably 5 to 30, especially 10 to 20 parts, and typically 12 to 15 parts, by weight per 100 parts of polyol.
The article is preferably in the form of a garment, which is more preferably in the form of a support for a part of the human or animal body where discomfort is suffered. However, the article may be an item of seating or bedding, for example, a cushion, bean bag (especially suitable for children), pillow, quilt, mattress, sleeping bag, soft-furnishing, office furniture (especially chairs), seats in aircraft, trains and automobiles, slippers and shoes and shoe, slipper and boot insoles. As a cushion, it may, in particular, be used by drivers of motor vehicles who, especially on long journeys, are susceptible to back pains. Considerable relief may be provided by such cushions. As a pillow or cushion, the article may serve to replace a conventional hot water bottle in view of the warm glow generated by it.
For some applications envisaged where copper foam may be used in cushions, seating and bedding, etc, within the home, then the foam would be required to comply with xe2x80x98The Furniture and Furnishings (Fire)(Safety) Regulations 1988 (amended in 1989 and 1993)xe2x80x99.
Garments in accordance with the invention may be constructed not only for treatment of the human body, but also for treating animals suffering from arthritis and rheumatic conditions similar to humans, for example, horses and dogs.
The garment may be a support for a part of the human or animal body or may be an entire article of clothing, for example, a warmer jacket or vest or gloves.
When the garment is a support for a part of the human body, any of at least the following can be supported to provide comfort and relief, namely the neck, left and right shoulder, double shoulder (including the centre of the back), elbow, forearm, wrist and palm, wrist, hand and fingers (glove), small of back, hip (left or right), hip and back combined, thigh, knees, calf, ankle joint, whole ankle and foot and separate toes and fingers (e.g. a finger stall).
It is found surprisingly that a considerable comforting heat is generated by the article, which need not come into contact with the skin of the user and can be separated from the user by, for example, clothing. Thus, in contrast to the principles outlined in GB-A-1581586 and GB-A-2133287, which rely upon generation of sweat (occasioning discomfort in this respect), the article in accordance with the invention allows the generation of a dry, comforting, heat.
The articles, especially garments, are especially suitable for use at night, while the user is at rest or in bed.
The cover is preferably a woven fabric, more preferably of a light breathable fabric such as cotton, muslin, polyester or polyester/cotton blend.
Where the cover is a lightweight fabric, especially cotton, this allows easy transference of the special heating properties of the copper-laden foam.
However, the article may additionally include an additional removable casing of, e.g. muslin, to protect the article and keep it clean.
Either the cotton cover or the casing may be suitably decorated.
The amount of relief from pain and inflammation experienced will vary from person to person. The other factors which may play a part are the number of consecutive nights that a garment or garments are worn and to some degree the amount of copper incorporated into the foam in terms of weight of copper.
When the article is in the form of a garment, it is preferably constructed from a fabric, covering the foam, which fabric has opposite side regions each having respective fastening means cooperable with one another on folding the fabric to allow the fabric to surround at least a part of the wearer.
More preferably, one opposite side region of the fabric has releasable adhesive means on a front surface of the fabric cooperable with releasable adhesive means on a rear surface of the other opposite side region of the fabric.
One example of a support garment is an ankle or knee support which, at least in use, has a generally tubular construction conforming with the shape of the ankle or knee.
Another example is a neck support which, at least in use, has a generally tubular construction to the shape of the neck.
Yet other examples are a support for the hip adapted to extend from the hip to the thigh on at least one side of the wearer and additionally including bands adapted to be secured, by fastening means, around the waist and thigh respectively, and a support for each shoulder adapted to fit around an upper part of the wearer, over the shoulders, and additionally including respective arm straps depending from an edge of the fabric and adapted to be secured, by fastening means, around respective arms.
In each of the above support garments, the fastening means preferably comprises respective cooperable strips of hook and loop fastenings, commercially available as xe2x80x9cVelcroxe2x80x9d, one disposed on a front surface along one of opposite side regions of the fabric and another disposed on a rear surface along the other side region. The strips may be so located that they cooperate to hold the garment comfortably but securely in position around the wearer.
As previously mentioned, the foam in the articles is preferably a high resilience MDI foam. This offers the following advantages:
a) good physical properties; and
b) good index response, i.e. foam hardness, flexibility and comfort can be varied significantly dependent on the amount of MDI isocyanate used.
Particular advantages associated with garments embodying the invention are as follows:
(a) The garments can ease, reduce and in some cases remove the pain associated with arthritis, rheumatism and related joint and limb ailments.
(b) To have this effect, an appropriate copper-foam filled garment is best worn overnight during the sleeping hours. However, the garments may be designed so as to be sufficiently soft and comfortable to be worn throughout night and day, thus allowing the maximum time for the presence of the copper to be effective.
(c) The copper-foam lends itself to be readily used as a pliable, breathable filling enclosed in light cotton-type fabrics to form various coverings or enclosing garments for joints, limbs and all body parts which are light, soft and comfortable enough to be worn throughout the night while sleeping. In this foam medium, the copper can be taken to any part of the body in the form of a comfortable garment, without any skin discolouration, as is evident when metallic copper is worn next to the skin.
(d) The copper presence can be spread easily and comfortably around the required area, and the garment creates a warm environment around the area. Thus, the wearing of a copper-foam filled garment also creates a heat where it is worn, which in its own right has a comforting effect.
(e) Copper-loaded foam can be cut into numerous templates and designs and enclosed in light breathable fabrics such as muslin, cotton or polyester/cotton and made into garments which cover and/or enclose all the various parts of the body.